pthread_mutexattr_init,         pthread_mutexattr_destroy,
       pthread_mutexattr_setkind_np, pthread_mutexattr_getkind_np
       - mutex creation attributes

SYNOPSIS

       #include <pthread.h>

       int pthread_mutexattr_init(pthread_mutexattr_t *attr);

       int pthread_mutexattr_destroy(pthread_mutexattr_t *attr);

       int       pthread_mutexattr_setkind_np(pthread_mutexattr_t
       *attr, int kind);

       int pthread_mutexattr_getkind_np(const pthread_mutexattr_t
       *attr, int *kind);

DESCRIPTION

       Mutex  attributes can be specified at mutex creation time,
       by passing a mutex attribute object as second argument  to
       pthread_mutex_init(3).   Passing  NULL  is  equivalent  to
       passing a mutex attribute object with all  attributes  set
       to their default values.

       pthread_mutexattr_init  initializes  the  mutex  attribute
       object attr and fills  it  with  default  values  for  the
       attributes.

       pthread_mutexattr_destroy   destroys   a  mutex  attribute
       object, which must not be reused until  it  is  reinitial-
       ized.   pthread_mutexattr_destroy does nothing in the Lin-
       uxThreads implementation.

       LinuxThreads supports only one mutex attribute: the  mutex
       kind,  which is either PTHREAD_MUTEX_FAST_NP, for ``fast''
       mutexes, or PTHREAD_MUTEX_RECURSIVE_NP, for  ``recursive''
       mutexes.  As  the  NP  suffix  indicates,  this  is a non-
       portable extension to the POSIX standard and should not be
       employed in portable programs.

       The  mutex  kind  determines  what  happens  if  a  thread
       attempts  to  lock  a   mutex   it   already   owns   with
       pthread_mutex_lock(3).   If  the  mutex is of the ``fast''
       kind, pthread_mutex_lock(3) simply  suspends  the  calling
       thread forever. If the mutex is of the ``recursive'' kind,
       the call to pthread_mutex_lock(3) returns immediately with
       a success return code. The number of times the thread own-
       ing the mutex has locked it is recorded in the mutex.  The
       owning  thread  must call pthread_mutex_unlock(3) the same
       number of times before the mutex returns to  the  unlocked
       PTHREAD_MUTEX_FAST_NP.

       pthread_mutexattr_setkind_np sets the mutex kind attribute
       in attr to the value specified by kind.

       pthread_mutexattr_getkind_np  retrieves  the current value
       of the mutex kind attribute in attr and stores it  in  the
       location pointed to by kind.

RETURN VALUE

       pthread_mutexattr_init,    pthread_mutexattr_destroy   and
       pthread_mutexattr_getkind_np always return 0.

       pthread_mutexattr_setkind_np returns 0 on  success  and  a
       non-zero error code on error.

ERRORS

       On error, pthread_mutexattr_setkind_np returns the follow-
       ing error code:

       EINVAL kind   is   neither    PTHREAD_MUTEX_FAST_NP    nor
              PTHREAD_MUTEX_RECURSIVE_NP

AUTHOR

       Xavier Leroy <Xavier.Leroy@inria.fr>

SEE ALSO

       pthread_mutex_init(3),              pthread_mutex_lock(3),
       pthread_mutex_unlock(3).